The discovery of a 50-year-old human tissue sample in an African university shows that HIV/AIDS pandemic in humans originated at least three decades earlier than previously thought.
Michael Worobey, an evolutionary biologist at the University of Arizona, Tucson, and lead author of the study suggests that AIDS may have been triggered by rapid urbanization in west-central Africa during the early 20th century and the virus most likely started circulating among humans in sub-Saharan Africa sometime between 1884 and 1924.
For the study, researchers analyzed tissue samples collected between 1958 and 1960 from Kinshasa in the Democratic Republic of the Congo. One of them, acquired in 1960, contained bits of HIV-1 RNA, the virus's genetic material. and uncovered the second-oldest genetic sequence of HIV-1 group M. They used this and other HIV-1 genetic sequences to construct a family tree of the origin of the viral strain and to estimate the time of origin of HIV-1 group M, National Geographic news reports.
This 1960 virus is the second-oldest known HIV-1 group M genetic sequence, with the oldest being a 1959 blood sample from a man also from Kinshasa. The researchers compared the 1960 virus with the oldest known HIV-1 strain, which was obtained in 1959 and evolved independently of the 1960 variant. The results indicated that the 1960 version was significantly different.
After constructing an evolutionary family tree of the HIV-1 virus, made up of both the 1959 and 1960 strains along with more than a hundred modern viral sequences, it was found that the 1960 strain must have been evolving for at least 40 years to account for the number of differences from the 1959 strain.
The research also traced the most recent common ancestor of both strains to 1908. The finding will help bring about better treatments or even a cure for the virus which causes AIDS, researchers say. The team's findings appear in Wednesday's issue of the journal Nature.